This invention relates to poly-N,N-hydroxyalkylamides of polybasic carboxylic acids and to a process for their production. These polyamides are particularly useful as cell-opening components in the production of highly elastic polyurethane foams.
Experience in the commercial production of highly elastic polyurethane foams has shown that, despite a high level of technical development, production still involves risks in regard to foam quality. More specifically, such foams are prone to shrinkage which results in an uneven distribution of mechanical properties over the cross-section of the foam block. The entire surface of the foam may be so seriously affected by this compression phenomenon that the product foam is rendered virtually useless.
In the production of cold foams, it has been standard practice to counteract some of the shrinkage and cell size problems by addition of stabilizers. (See for example U.S. Pat. No. 3,748,288 and German Offenlegungsschrift Nos. 22 10 721 and 24 54 049), although this causes deterioration of the mechanical properties of the foams, particularly in their compression hardness. Thus, although German Offenlegungsschrift No. 21 03 730 describes the production of open-cell foams by the use of polyalkylene polyamines as incorporatable catalysts, organo tin catalysts could not be used on account of the shrinkage effects which they produce. (Note page 6, paragraph 2 of the Offenlegungsschrift (specification as laid open)). It would therefore be advantageous to have a process in which the cell-opener would make it possible not only to maintain the mechanical property level, but to improve mechanical properties through use of metal catalysts without reducing the level of open-cells or increasing the tendency towards shrinkage.
British Pat. No. 1,032,873 describes poly-N,N-hydroxyalkylamides of polymeric fatty acids corresponding to the following formula ##STR3## in which R is the dimerized, trimerized or polymerized residue of fatty acids containing from 8 to 24 carbon atoms. These compounds were used with polyisocyanates for the production of coatings. They were not, however, used as cell-opening additives in the production of polyurethane foams.